The present invention generally relates to a compact optical disc cartridge of a type accommodating therein a rewritable optical disc such as, for example, an erasable optical disc, a magnetooptical disc or a phase-changeable optical disc. More particularly, the present invention relates to a safety device in the optical disc cartridge for preventing information, recorded or otherwise stored on the rewritable disc, from being erased inadvertently.
Optical disc cartridges are available in a variety of types. Of those optical disc cartridges, the optical disc cartridges utilizing a rewritable optical disc such as, for example, an erasable optical disc, a magnetooptical disc or a phase-changeable optical disc require a safety device installed therein for preventing information recorded or stored on the rewritable optical disc from being erased inadvertently. The safety device generally comprises a movable element that moves selectively between enabled and protected positions. While information can be recorded or overwritten on the optical disc when the movable element is moved to the enabled position, the information recorded, or otherwise stored on the optical disc can be neither recorded nor overwritten in any way whatsoever when the movable element is held at the protected position. To move the movable element in this way, the movable element has a safety lug accessible to the user.
By way of example, the rewritable optical disc cartridges generally comprises a generally square flat casing including top and bottom panels and four side walls. all assembled together to define a disc chamber therein. An optical disc is rotatably housed within the disc chamber. The safety device is operatively accommodated within one of four, generally triangular corner spaces each defined inside and at a corner region of the disc casing. One of the four side walls of the optical disc cartridge that is adjacent the triangular corner space where the safety device is housed has an opening defined therein with the safety lug held in position accessible from outside of the optical disc cartridge so that the user can manipulate the safety lug.
Other than the safety device, the optical disc cartridge has two or more positioning and identifier holes defined in the bottom panel and positioned adjacent two or more corner regions of the disc casing. The positioning holes are cooperable with corresponding positioning pins installed in an optical disc player and are utilized to set the optical disc cartridge in position ready to establish an interactive relation between the optical disc and an optical read/write head once the optical disc cartridge is loaded in the optical disc player. On the other hand, the identifier hole or holes are utilized to allow the optical disc player to recognize the specification of the optical disc cartridge loaded therein. The specification of an optical disc cartridge includes the recording capacity of the optical disc and/or the optical characteristic (e.g., erasable or non-erasable) of the optical disc. It is pointed out that where the optical disc housed in the cartridge is a non-erasable type, the optical disc cartridge may not be provided with the safety device.
The optical disc cartridge also has a sensor hole defined at a location aligned with the movable element of the safety device, which hole is selectively opened or closed by the movable element. By way of example, the sensor hole may left open when the movable element is in the protected position, but be closed when the movable element is in the enabled position. The movable element employed in the prior art safety device is generally in the form of an elongated slide piece linearly slidable along the side wall of the disc casing between the enabled and protected positions.
Considering that the optical disc cartridge is getting. compact and compact and a currently commercially available MD (Mini-Disc) cartridge has a size of about 7.2xc3x976.8 cm with the erasable optical disc being about 6.4 cm, the corner spaces available in the optical disc cartridge are correspondingly getting smaller. The smaller the corner spaces, the smaller the safety device and, thus, the smaller the stroke of movement of the slide piece. If the slide piece is reduced in size, the safety lug must also be reduced in size in order to secure a required stroke of movement for the slide piece. The smaller the safety lug, the more difficult the user feels to manipulate it.
In order to ensure the movable element to be assuredly moved between the enabled and protected positions even though the safety lug is minute, the Japanese Laid-open Patent Publication No. 10-338286, for example, discloses a cartridge storage casing for accommodating a rewritable optical disc cartridge when the latter is not in use, which storage casing is provided with an operating pawl that triggers the slide piece externally through the safety lug while the optical disc cartridge is within the cartridge storage casing. Although the safety system disclosed in this patent publication appears satisfactory, the external operating piece disclosed in the above mentioned publication would no longer work out if the optical disc cartridge is further reduced in size, accompanied by corresponding reduction in size of the movable element inside the. optical disc cartridge. More specifically, if the external operating piece is reduced in size in correspondence with reduction in size of the movable element, difficulty would be encountered in securing a sufficient physical strength in the external operating piece, or the external operating piece would become susceptible to damage when the optical disc cartridge is inadvertently subjected to impacts.
The possibility of the external operating piece being excessively reduced in size may be eliminated if the cartridge storage casing is assembled to a size slightly larger than the optical disc cartridge. However, since demands have arisen for the optical disc cartridge to be manufactured in, a further reduced size while efforts have been made along with it to increase the information recording density of an optical disc, increase in size of the cartridge storage casing is limited.
Accordingly, the present invention has for its primary object to provide an improved optical disc cartridge wherein the safety device makes use of a switching element, in place of the slidable element such as employed in the prior art optical disc cartridges, to thereby reduce the space occupied inside the optical disc cartridge by the safety device, so that the optical disc cartridge as a whole can be manufactured in a further compact size.
Another object of the present invention is to provide an improved optical disc cartridge of the type referred to above, wherein maximized utilization is made of at least one of the limited corner spaces available in the optical disc cartridge to enable the safety device to be accommodated therein snugly.
A further object of the present invention is to provide an improved optical disc cartridge of the type referred to above, wherein a tubular boss positioned inside the optical disc cartridge so as to surround one of the positioning holes for reinforcing a peripheral lip region around the positioning hole is advantageously utilized for the support of the switching element for movement between the enabled and protected positions.
A still further object of the present invention is to provide an improved optical disc cartridge of the type referred to above, wherein means is provided for-enabling the user to ascertain the position of the switching element from outside of the optical disc cartridge.
A still further object of the present invention is to provide an improved optical disc cartridge of the type referred to above, wherein means is provided to lock the switching element at any one of the enabled and protected positions.
In order to accomplish these and other objects of the present invention, there is provided a disc cartridge accommodating therein an erasable disc-shaped recording medium which includes a disc casing having a disc chamber defined therein for rotatably accommodating the recording medium. The disc casing has a sensor hole and a slot defined in first and second wall portions of the casing that are opposed to each other, so as to extend completely across a thickness of the corresponding wall portion. The disc cartridge also includes a safety device disposed within the disc casing for preventing information recorded on the erasable recording medium from being erased inadvertently.
The safety device includes a bearing bushing positioned at a location spaced from the sensor hole and formed within the disc casing so as to protrude from the first wall portion towards the second wall portion, and a switching element movably accommodated within the disc casing and having first and second ends opposite to each other. The first end of the switching element is rotatably connected with the bearing bushing for angular movement between first and second operative positions. The sensor hole is adapted to be closed by the second end of the switching element when the latter is angularly moved to the first operative position. An operating piece is provided on the switching element so as to extend therefrom and terminate in the slot in the second wall portion. This operating piece is movable within the slot in correspondence with the angular movement of the switching element between the first and second operative positions.
The first and second operative positions of the switching element may be protected and enabled positions, respectively. Accordingly, with the switching element held at the protected position, the recording medium within the casing is advantageously protected from being inadvertently erased.
According to the present invention, the safety device requires a relatively small space for installation thereof within the disc casing and, yet, the switching element forming a part of the safety device can have an increased size, as compared with the prior art safety device utilizing the slide element. The switching element having the increased size is robust enough to ensure the reliability of the safety device.
The first wall portion of the disc casing may have at least one positioning hole defined therein, in which case the bearing bushing is preferably formed on the first wall portion in coaxial relation with the positioning hole.
The switching element employed in the safety device of the present invention is preferably of a structure including a bearing ring rotatably mounted on the bearing bushing, a trunk connected with the bearing ring so as to extend radially outwardly therefrom, and an arm connected with the trunk so as to extend angularly therefrom and adapted to selectively open and close the sensor hole. The operating piece is fixedly mounted on this arm.
The bearing bushing may have a cutout formed therein so as to render the bearing bushing to represent a generally C-shaped configuration, Where the bearing bushing is of the generally C-shaped configuration, the switching element may include a bearing ring rotatably received within the bearing bushing, a. trunk connected with the bearing ring so as to extend radially outwardly therefrom through the cutout, and an arm connected with the trunk so as to extend angularly therefrom and adapted to selectively open and close the sensor hole.
Preferably, the operating piece has a free end face situated within the slot and has an operating recess defined in the free end face for receiving a tip of an instrument when the switching element is to be moved between the first and second operative positions, so that the user can easily manipulate the switching element through the operating piece with the aid of the instrument such as a ball-point pen.
Also preferably, edges of respective portions of the second wall portion confronting opposite ends of the slot are chamfered to define a generally rounded depression, the bottom of which is inwardly curved and inclined from an outer surface of the second wall portion towards the slot, to thereby facilitate an easy access to the operating piece when the user desired to move the switching element from the first operative position towards the second operative position, and vice versa.
The disc cartridge embodying the present invention may be additionally provided with a display means for providing a visual indication of a position of the switching element relative to the sensor hole. This display means may be formed on the bearing ring and is capable of assuming one of two distinct states corresponding to the first and second operative positions of the switching element. To enable the position of the display means to be viewed from outside, a third wall portion of the casing lying perpendicular to any one of the first and second wall portions is formed with a viewing window.
The display means may comprise two areas of the bearing ring that correspond respectively to the two different states of the display means, said two areas being of a different color. Alternatively, the display means may comprise a display cutout formed in a portion of the bearing ring and an outer surface area of the bearing ring neighboring the display cutout. In this alternative embodiment, the display cutout permits a portion of the bearing bushing to be exposed to outside of the disc casing through the viewing window when the switching element is moved to the first operative position, but the outer surface area of the bearing ring is aligned with the viewing window when the switching element is moved to the second operative position.
Preferably, an outer edge of a peripheral lip region of the third wall portion that surrounds the viewing window is chamfered so as to flare outwardly to thereby enhance viewability from outside of the disc casing.
The disc cartridge embodying the present invention may be additionally provided with detent means intervening between the switching element and the first wall portion for clicking the switching element to any one of the first and second operative positions. This detent means may include an elastically deformable detent piece integral with the switching element, a detent protuberance integral with the deformable detent piece so as to protrude towards the first wall portion and two spaced apart detent recesses defined in the first wall portion and spaced a distance corresponding to a distance between the first and second operative positions of the switching element.
According to the present invention, the switching element moves angularly in a generally sector-shaped space within the disc casing between the first and second operative positions. As is well recognized by those skilled in the art, the necessity of a generally rectangular space for the slide member used in the prior art safety device to move make it difficult to define in a wall of the disc casing a plurality of identifier holes for transmitting to a disc player information descriptive of the type or specification of the disc cartridge, at respective location clear from the rectangular space. In contrast thereto, the sector-shaped space allows those identifier holes to be relatively easily defined in the wall of the disc casing without being disturbed by the presence of the switching element. Accordingly, for a given space required, utilization of the limited space available within the disc casing can be maximized according to the present invention, allowing the present invention to provide a more compact disc cartridge having the safety device.